1. Field of the Invention
This invention relates to ink ribbon cassettes, and more particularly, to a method and apparatus for determining when a ribbon in a ribbon cassette should be replaced.
2. Description of Related Art
The use of ribbon cassettes in printers has become quite common. Ribbon cassettes are advantageous because they can be easily installed in and removed from the printer. A problem in the prior art is that it was difficult to determine when the ribbon cassette needed to be replaced. The printer would print data having a desired density during normal operation. However, the printer would print data having an undesirable density if the ink ribbon in the ribbon cassette did not have a sufficient ink content. This often resulted in the printer printing illegible data on a document before an operator was made aware that the ribbon cassette needed to be replaced. This was particularly true where the printer was not continuously attended by the operator. Any documents having illegible printing would have to be discarded and new documents would have to be reprinted.
There is, therefore, a present need to provide a means for automatically determining when to replace a ribbon cassette in a printer which means is inexpensive, easy to implement, and not time consuming to use.